1. Field of Invention
This invention relates to improved pipe couplings and is especially directed to improved means for coupling multi-layer pipe and the like.
2. Prior Art
As is well known, pipes for transporting fluids may be formed of metals, such as lead or copper, or of plastic, such as polyvinyl chloride. Unfortunately, copper pipe is quite difficult to solder and is usually thin-walled and, therefore, can easily be deformed accidentally. Furthermore, copper pipes are extremely difficult to solder or weld. On the other hand, lead and plastic pipes are easy to work with and, hence, are very popular with do-it-yourself plumbers. However, lead and plastic pipes have been found to sometimes release carcinogenic materials and, thus, are unsuitable for carrying domestic water and their use is prohibited by law in many places. To overcome these problems, multi-layer pipe has been proposed, having an inner layer of copper to protect the water and having an outer layer of plastic which is strong enough to prevent deformation of the copper liner and which provides the ease of working for each the plastic pipe is known. However, most of these multi-layered pipes require complex and expensive coupling devices and, even where this is not so, extreme care must be exercised in making joints and couplings with such multi-layered pipe or else the plastic coating will be exposed to the water and may contaminate it.
A search in the United States Patent Office has revealed the following references:
______________________________________ U.S. PAT. NO. INVENTOR ISSUED ______________________________________ 4,400,019 B. E. Fruck Aug. 23, 1983 4,556,240 T. Yoshida Dec. 3, 1985 4,709,946 J. J. Hunter Dec. 1, 1987 4,927,184 P. Bourot et al May 22, 1990 ______________________________________
Each of these references is subject to the limitations set forth above. Thus, none of the prior art pipe coupling devices have been entirely satisfactory.